(a) Field of the Invention
The present invention relates to an ink jet recording device, and more particularly, to an improvement of controlling an ink jet recording device for cleaning an ink jet slit of the ink jet recording head by removing foreign materials such as ink mists from the ink jet slit.
(b) Description of the Related Art
In an ink jet recording head of an ink jet recording device such as a printer or copying machine, the ink jet slit of the recording head for ejecting ink droplets onto a recording sheet is often closed or blocked by foreign materials such as ink mists, which causes malfunction of the recording head.
The foreign materials are usually removed by cleaning the ink jet slit during a recording operation of the recording head. A first cleaning operation is generally effected between the finish of a feed operation of a recording sheet and a start of the printing operation. After the printing is started, a timer counts the time length from the start of the printing, interrupts the length from the start of the printing, interrupts the printing operation and effects a second cleaning operation after a specified time length elapsed since the start of the printing. The printing and interrupting cleaning operations are alternately effected for the specified time intervals so long as the printing command continues.
Patent Publication JP-A-7(1995)-125228 proposes a cleaning process for the ink jet slit, wherein an ink ejection frequency during the printing operation is counted, and the start of the next cleaning operation is controlled based on the counted ejection frequency. The proposed method has an advantage in reducing the cleaning frequency during the printing operation to a minimum required for the ink jet slit.
In the proposed method as well as the conventional method, the start of the cleaning operation is judged by a computer or a controller which detect the timing of the cleaners by receiving a count signal and comparing the count with a specified value. The processing for the judgement in this manner by the computer generally reduces the throughput of the computer in processing other operations of the printer.
Moreover, there is a problem in that the cleaning operation during the interval between the printing operations tends to stain the recording sheet fed on the recording head and consumes a longer time length for the computer processing corresponding to the processing for the cleaning operation.